headcanon
”After being adopted by the Sanada house, I gained a mother… I was never really alone until I entered high school.”
From the drama CD "Daylight" on track 8 (you can hear it here at 33:16), Akihiko has mentioned that he was adopted by the Sanada family after the accident where his sister had deceased because of the unluck fate and at the age of 9. Which means, the surname "Sanada" is adoptive and his real surname remained unknown. It was never clearly-stated in game. It also has been stated in the certain official artwork (which can be seen in here.) and it is a possible fact within Akihiko's circumstances which hasn't been revealed clearly.
"No matter how much power you gain, it's meaningless. You're inevitably going to meet your end at the hands of a greater power."
Shadow Akihiko is the other part of Akihiko, which it has been believed his Persona has taken over him despite the user was giving up for it. He often to be seen as sarcastic and immature. While he generally has a playful nature, he easily flies off the handle whenever the person was off the limits. Although, he is perpetually bored and likes games; but he is more into mind games. He is reckless to a fault, losing his self-control and ambition; which was the reasons why he often to be offended.
He knew the real Akihiko hasn't gone over the death of his loved ones, instead he felt pissed because he was pretending to do it. Sometimes, he says something about the thrill for a fight and protecting someone are only as a cover for his weakness despite on how strong he looks like. Though, some of Akihiko's personalities are still remained inside the shadow itself, but only in a small occasion.
He knew the real Akihiko hasn't gone over the death of his loved ones, instead he felt pissed because he was pretending to do it. Sometimes, he says something about the thrill for a fight and protecting someone are only as a cover for his weakness despite on how strong he looks like. Though, some of Akihiko's personalities are still remained inside the shadow itself, but only in a small occasion.
"I have other interests rather than boxing, those made me feel fun whenever I feel bored after training."
After in his expedition to go around the world for his training in boxing, he has some other interests than the boxing itself, such as martial arts and ice skating. Martial arts he learned for another self-defense other than boxing, it should be effective enough but he is rarely to use it during battles--only in critical state. For ice-skating itself, he found it interesting and fun since his coach brought him into the ice rink for their fun during their expedition on training. Otherwise, it becomes his personal fun and feels enthusiastic whenever he wants to skate once again like the time he was during his expedition.